There is a growing scientific need to research extreme underwater environments at depths of about 11,000 m (36,000 feet). Particularly, there is an interest in studying subduction zones found in the deepest oceanic trenches around the world. These trenches are home to reserves of metallic ores, and house unique biological communities that flourish in these extreme conditions. There is also a growing interest in investigating magmatic, hydrothermal and volcanic activity in these deep locations and to perform oil exploration and production.
Existing robotic deep submergence vehicle systems have excellent capabilities and provide critical, routine access to the seafloor primarily in ranges up to 6,500 m. These systems utilize tether systems (attached to surface vehicles such as ships) that generally prevent full operation of devices at depths of past 7,000 m or so. Such prior art cable systems include steel cable systems. This steel cable tether is limited by the weight of the cable that increases substantially with increasing length of cable. At one point the weight of the cable begins to exert a force on the support ship that is well past the allowable limits. Other prior art systems include Kevlar cable systems. These Kevlar systems offer high strength to weight ratios. However, they are very expensive and have limited lifetimes. Moreover, the cross-section of the cables are relatively large resulting in a high-drag system that the undersea vehicle cannot easily move horizontally or tow. Further, the prior art systems also require large support ships that have typically, custom made cable handling systems. These support ships are costly to operate and to equip with the needed cable handling systems.
Accordingly there is a need for improved tether capable of deploying and securing vehicles at depths of up to 11,000 m for extended periods of time.